Ben Carson’s campaign turned into a kaleidoscope of oddities last week: The retired neurosurgeon made fanciful claims about the purpose of Egyptian pyramids and the political experience of the Founding Fathers. He insisted that he was, in fact, a violent youth, but admitted that he wasn’t, in fact, offered admission to West Point—both key highlights of his autobiography. But amid all the attention being paid to his personal background, it’s easy to overlook what Carson is actually running on. Of all the GOP candidates, Carson has put forward the most radical ideas for overhauling country’s entitlement programs. And while he's lately begun to clumsily retreat to more moderate alternatives, they don't add up any more than his attempts to explain the factual holes in his autobiography. While his past will surely provide rich fodder for Tuesday night's fourth GOP debate, it's what Carson proposes for America's future that truly needs more critical attention. 

Carson originally proposed to scrap Medicare and Medicaid entirely—a genuinely radical idea, and one with massive policy and political risks. Under his plan, every American would receive a cradle-to-grave health savings account with an annual $2,000 government subsidy, which family members could share. But after the third debate two weeks ago, Carson began running away from that old idea, which had been coming under increasing attack by fellow Republicans, particularly Donald Trump. “Ben wants to get rid of Medicare, Trump said last week. "You can’t get rid of Medicare. It would be a horrible thing to get rid of.” 

Carson has begun to roll out an alternative that avoids the political liabilities of blowing up the entire system. But his account of the changes he’s made has been as confusing as the West Point saga. A few days before the last debate, Carson was already claiming on Fox News Sunday that his original plan for entitlement reform had been “gone for several months now." That confused host Chris Wallace, who—like most of those watching—had definitely not been under that impression. Though he remains hazy on the details, Carson’s new scheme could also be massively disruptive, not only undermining care but also running up costs for the government. 

Under Carson’s new plan—at least, from what can be sussed out from his statements—the traditional government programs would stay in place, but people would have the alternative to opt out with private Health Savings Accounts they could use to purchase their own coverage. Unlike his original plan, however, not everyone would get a subsidy in this one. Many of the details remain murky, and Carson’s campaign says a full-blown proposal is forthcoming. But based on his remarks so far, Carson seems to be suggesting that if you qualify for Medicare or Medicaid, you could choose to have the government money that would have paid for your health care to go directly to a private savings account instead. “I would never get rid of the programs. I would provide people with an alternative,” Carson said on Fox News Sunday. “I think they will see that the alternative that we're going to outline is so much better than anything else that they will flock to it.” 

But Carson’s alternative could create a whole host of problems. Those who pick HSAs would likely face very high deductibles and co-pays, which could lead them to forgo necessary care. At the same time, the cost of government health programs could end up rising as well. Healthier people would likely opt out if they could receive cash in private accounts, while sicker people would probably stick with traditional Medicare and Medicaid. “The new plan runs the risk of costing the government more than the current system, since people could game a two-choice system, sticking with a savings account when their spending is low, and switching to a government program once their medical costs rise,” writes The New York Times’s Margot Sanger-Katz. 

If Carson’s original plan took a sledgehammer to Medicare and Medicaid, his alternative risks seriously weakening the programs. Despite his medical credentials, Carson seems confused about the very basics of the health care system. In a recent interview, he said that Medicare and Medicaid fraud was costing taxpayers “half a trillion dollars,” a truly astonishing estimate given that the total cost of both programs is $980 billion, as Mother Jones’s Kevin Drum points out. (Experts estimate that the real cost of Medicare and Medicaid fraud could be about $98 billion.) 

In previous Republican debates, candidates have treated questions about the factual reality of their policy ideas as an inconvenience to be brushed aside—or as evidence of a media conspiracy to smear conservatives. But it wouldn't be surprising on Tuesday night, given Carson's standing in the polls and the scent of his blood in the water, if other Republican candidates go after him on Medicare and Medicaid far more aggressively. Carson won't be the only likely target: Former Florida Governor Jeb Bush and Senator Marco Rubio have both embraced House Speaker Paul Ryan’s contentious “premium support” proposal, which would give seniors a set amount of money to buy private insurance or traditional Medicare.

Carson’s original idea to overhaul Medicare was far more comprehensive, however, and his new idea is significantly more confusing than his rivals’. Though he’ll likely spend much of Tuesday night defending himself on other scores, his credibility is also on the line when it comes to his policy proposals. We had a preview of what's to come in the last debate, when Carson was pressed to explain his wild-eyed idea to scrap the current tax code in favor of a ten-percent flat tax. He responded by denying that this was ever his position to begin with, then refused to accept the basic facts behind the idea.

He’s already started to use the same cop-outs when it comes to his health-care ideas, acting as if he had never proposed to get rid of Medicare. This, ultimately, is why Carson’s trouble with truth-telling really does matter: His fuzzy relationship with the facts doesn't stop with his youth. 

The original story referred to Tuesday as the "third GOP debate." It is the fourth debate.